First of all, please keep in mind that there's NO short cut in the game on farming, you will need to spend hours and hours of time to grind stages. So here we go.

1. If you're not planning to spend tons of money on the game, at least buy the $4.99 package that gives you 60 gems a day for 30 days, that's 1800 gems!

2. Please save your gems for SP potions and recharging the extract points AFTER you've done your first 10+1 draw. In my opinion, it's better to have a strong team 1 to start the game than having 5 not-so-strong teams.

3. Concentrate on ONE hero at a time. You should get ALL 5 heroes to 4 star in normal mode. With five 4-star heroes, you should be able to get through normal mode. Don't waste time and potions to get heroes to 5 star in normal mode because you can get much more fragments in hero mode.

4. When choosing a stage to farm, look at both drop list and max level rewards. For example, if you are farming for wood fragments and at the meantime, you also have a fire type hero, then you may consider a stage that drops wood monsters with fire fragments as max level reward. On the other hand, if you're trying to level up your heroes while farming fragments, then choose any boss stages because you get one extra wave of monster, and that means more exp.

5. Higher stages have higher chances for higher star monsters. In normal mode, you will only get 1 star monsters. In hero mode, you will start getting 2 and 3 star monsters AFTER stage 10. In legend mode, you will only get 2 and 3 star (haven't seen any 4 star yet as of 17-2) monsters on the map.

6. There's a bonus in extracting fire type monsters as of 8/12, I've been trying to extract all types of monsters everyday to see how often do this bonus changes. As for the past 11 days, it's still fire.

Below is some statistic I've done for farming essences:

As in hero mode (in stage 11 and 12), 90 stamina would get about 100~120 fragments for NON bonus elements.